'Game of Thrones:' A Look at Season 3's New Faces and Characters

Mance Raydar (Ciaran Hinds) and Lady Olenna Tyrell (Diana Rigg) in "Game of Thrones" Season 3. (Helen Sloan/HBO)

SPOILER ALERT: This post contains storyline and character spoilers for the third season of "Game of Thrones."

With 27 series regulars and hundreds of guest stars, day players, and extras wandering in and out of Westeros and points beyond, keeping track of who's who on "Game of Thrones" is almost as big a feat as planning the Battle of Blackwater Bay. That task isn't going to get any easier when Season 3, which was shot by three units across five countries and promises plenty of fresh faces, begins March 31 on HBO.

Arguably, the most major addition to the cast was Ciaran Hinds. One, his resumé is as respected as Tywin Lannister's and almost as long as the feared coming winter, with "Rome," "Harry Potter," "Political Animals," and "There Will Be Blood" among the highlights. Two, he is portraying Mance Rayder, the ex-Night's Watchman who united 90 clans into one Wildling army currently moving in on the Wall. Rose Leslie (Ygritte) admitted at the junket last week in Beverly Hills to being a tad starstruck as "we've been watching him from a young age. Phenomenal."

Kit Harington, whose Jon Snow is trying to infiltrate the camp and must get Rayder to trust him, was also in awe. "He's a wonderful, wonderful man, and for someone who hadn't read the books and hadn't even seen the show when he joined and did his first few scenes, he nailed the character. That's the mark of the man's genius and genius of the writing."

[Related: How Kit Harington's Lost Keys Almost Derailed 'Game of Thrones' Season 3]

Rayder isn't the only new force Jon Snow has to reckon with. When he walks into their camp in the season premiere, Jon comes face-to-knee with a bona fide giant. Harington and Leslie, however, were greeted instead by a long bar with an orange ball at the end being jogged across the set to establish a common sightline for the captive and his ginger captor. They were quick to remind that it wasn't all CG trickery. "Don't be fooled. That was a 7-foot-1 tall man, Ian, in a costume and massive boots. He was quite impressive in it. If they just filmed that, it would look like a giant," Harington explained. Leslie added, "[It took] four hours to get into prosthetics."

Fellow brother in black John Bradley (Samwell Tarly) recalled his meeting with the giant, who we have surmised -- HBO wouldn't confirm -- is played by Ian Whyte, an ex-professional basketball player who was already seen in past seasons as a White Walker and Lannister disciple Ser Gregor Clegane. "It looks kind of surprisingly realistic in real life," Bradley recounted. "We were all at the same hotel. I came down to breakfast, was getting my toast, and thought this is the only project in the world where this thing can appear next to you at breakfast and you just go, 'Morning, Ian.'"

[Related: Emilia Clarke and Kit Harington on the Cover of EW]

Viewers will also say hello to a new face at court, Margaery Tyrell's sarcastic and scheming grandmother, Lady Olenna, who will be brought to the screen by Diana Rigg (TV's "The Avengers"). "Dame Diana Rigg. Let's give her her full title," gushed Natalie Dormer who admitted it was "pretty cool" to be even faux related to the Bond Girl. The minute Olenna appears on screen, one gets the sense that she is also playing the game of thrones to win. "[Margeary] has been trained to be cool, calm, and practical by her grandmother."

The Queen of Thorns may wind up an ally to King Joffrey's castoff betrothed Sansa Stark (Sophie Turner) as well. Turner also showed unwavering respect for the Emmy and Tony winner. "I can totally draw parallels from my reaction to Diana Rigg and Sansa's reaction to Lady Olenna. You meet Diana Rigg and you know you've met Diana Rigg because she is this huge personality, a total veteran in the business and respected. She knows the business inside and out. And when Sansa meets Olenna, she is very educated and knows how to play the game. People totally look up to her and are pretty terrified of her. And everyone looks up to Diana. It's like the reaction you get around Charles Dance. You can't help but just watch her and be blown away."

Bran Stark (Isaac Hempstead Wright) and his Winterfell-fleeing band of misfits will join forces with a brother-and-sister duo whose father was rebellion buddies with Ned Stark. Meera (Ellie "Upstairs Downstairs" Kendrick) is the muscle and Jojen (Thomas "Love Actually" Brodie-Sangster) is the brains as he educates Bran about his prophetic dreams. "It was nice to have some new faces because it brings a new dynamic to the group that wasn't there before," Hempstead Wright commented.

[Related: Second-by-Second Breakdown of 'Game of Thrones' Trailer]

Other newcomers of note include Mackenzie Crook, Paul Kaye, and Nathalie Emmanuel. Crook, best known for the original "Office" and the "Pirates of the Caribbean" franchise, will be seen as wilding raider Orell, who has the ability to commune with animals. Given Orell's minor character status in the books juxtaposed with the high-profile casting, there's a lot of Internet speculation that Orell is actually an amalgamation of characters. Kaye has been charged with bringing Thoros to life. Thoros marches with the Brotherhood Without Banners and is part of the Arya Stark tangent. Emmanuel, who had a recurring role on the British soap "Hollyoaks," was cast as Missandei, an enslaved translator who crosses paths with Daenerys Targaryen.

Don't feel like a lesser fan if facial recognition fails you. The scope of the series is so huge that there are still actors in major roles who've gone three seasons without ever meeting on screen or in real life. Gwendoline Christie (Brienne), who was tasked with escorting king slayer Jaime Lannister back to King's Landing, was finally introduced to Jaime's on-screen sister/lover/baby mama Lena Headey (Cersei), less than two weeks ago at the Los Angeles premiere party. "Unfortunately for me, that was the first time I properly met Lena," Christie said. "Not everyone is always available for the table read [at the beginning of the season] or filming in the same place at the same time."

[Related: Gwendoline Christie Too Pretty for 'Game of Thrones'?]

Besides, in this dire wolf-eat-dire wolf world, it's probably best not to get too attached to a character anyway. That's also a lesson the cast has had to learn. Harington explained, "You have to say goodbyes as you go along and kind of move on. You get immune to it in the end."

"Game of Thrones" Season 3 premieres Sunday, 3/31 at 9 PM on HBO.